New Construction Metal Roof Installed Over Purlins

Measuring the outer perimeter existing profile of the roof panel skylight locations and modularity with the new metal roof rib spacing and identifying.

New construction metal roof installed over purlins.

Place corner pieces where panels will meet bends at the edge of the roofing. Purlins are 2 by 4 feet and are installed much like metal roofing. Metal roof purlins are installed horizontally under metal roofs. Use 1 1 4 inch nails to cover the outline of the roof with strips of metal eave flashing also called edging.

The actual installation of metal roofs on 1x or 2x purlins has been done for decades on ag and wood framed commerical buildings. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. The topic we want to discuss today is the purlin installation. They re also simple to install.

A standard retrofit sub framing system will not allow a positive attachment to the existing roof purlins. Installing a metal roof is a complicated process with many details. Its use on residential projects is far less common but has been done a lot especially in rural areas. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.

If there are gutters installed on the eaves the eave flashing should be installed to overhang the lip of the gutter by about 1 2 inch. The spacing of your purlins depends on the expected snow and wind load. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern. Our metal roof and wall panels qualify for underwriters laboratories ul class a fire rating ul 90 wind uplift rating and class 4 ul impact resistance hail rating.